New insights into the interaction between bacterioplankton community and dissolved organic matter driven by river...

River damming profoundly alters hydrological connectivity, reshaping dissolved organic matter (DOM) composition and bacterioplankton community dynamics in aquatic ecosystems. However, the effects of connectivity loss on DOM-bacterioplankton community interactions remains unclear. Here, we investigated the Chishui River basin to elucidate how dams-induced river connectivity modulate the relationship between DOM and bacterioplankton community. The result indicated that dam significantly altered DOM composition regardless of the level of river connectivity, while the bacterioplankton community structure was strongly influenced by connectivity gradients. Gammaproteobacteria dominated in low-connectivity reaches and were identified as keystone taxa that contributed to maintaining network stability. Partial least squares path modeling identified total nitrogen and electric conductivity as key drivers of bacterioplankton diversity. Increased bacterioplankton diversity at lower RCI negatively regulated DOM components, thereby altering DOM utilization pathways. Additionally, prolonged water retention under low RCI enhanced natural DOM transformation, directly promoting its utilization by bacterioplankton community. Our findings reveal that river connectivity critically governs microbial-carbon interactions, offering new insights into the cascading ecological effects of dam construction.